EUSTACHIAN TUBE GROWTH AND DEVELOPMENT: ANATOMY/FUNCTION The existing literature documents an important role for the Eustachian tube (ET) in the pathogenesis and/or persistence of Otitis Media (OM). Cross-sectional studies report a lower prevalence of OM in older children, a better ET pressure-regulating function in older children and age-related differences in ET form, length and width, and the vector orientation of the paratubal musculature. These growth-related changes in ET structural relationships are demonstrably predictive of increasingly more efficient ET function (F) and, because the ET and paratubal musculature are intimately related to the cranial base, the vector orientation of the ET system can be reconstructed from osteological or radiographic data. Together, these observations suggest that measurable, age-related changes in ET-paratubal muscle vector relationships are reflected in more efficient ETF and, by consequence, a decreased OM risk. The overall goal of the proposed longitudinal study is to evaluate the validity of this hypothesis. We plan to enroll a total of 90 children at 2 to 3 years of age (Group 1-30 with a history of recurrent actute OM, Group II-30 with a history of OM with effusion, and Group III-30 control) and to evaluate ETF (yearly) and measure craniofacial morphology (by yearly anthropometry, biyearly cephalometrics, MRI in a subset at age 4 and 6) over a 5 year period. The craniofacial measures will be used to reconstruct vector relationships of the ET system for each child and will be submitted along with the ETF results to Core C for analysis of the translational mechanism underlying the limitations imposed on ETF by craniofacial morphology. These data will be used to test the following hypotheses: 1) certain cephalometric measures of craniofacial morphology predict increased OM risk;2) correspondences to these measures are represented by non-invasive anthropometric measures;3) ETF variables discriminate between the different clinical presentations of OM;4) the mechanical properties of the ET are limited by the underlying form/structure of the craniofacial skeleton, and 5) growth and development of the craniofacial skeleton are associated with more favorable ET/paratubal muscle vector relationships which are then reflected in better ETF test results. In a subset of these children (10/group) selected for their ability to complete MRI testing without sedataion, MRI of the ET-ME system will be obtained at age 4 and 6 years. Data will be used to reconstruct the functional mechanics of the system for comparison among groups and also with the respective mechanics generated by the craniofacial measures. This Project represents the translation of past observational studies into a longitudinal clinical study that will, for the first time, test falsifiable hypotheses suggested by those earlier results. Study results may lead to the development and application of methods for the early identification of children "at risk" for OM, for the prognosis of disease course in young children and for alternative, patient-specific interventions to prevent/cure OM.